Tanning



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- v mzw YORKJI. 2., a coaronsnon or nnnawsma Specification or Letters Patent; Patented Sept. 13, 1921.

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naeogras. 4 Io Drawing. Application llledieptember 24, 1918. Serial Io. 255,477.

To all whom it concern: I I

Be it known t at I, JonnK. Toms, subject of the Kin of Great Britain, and a resident of N ewv ork cit ,in the county of New York and State of ew York, have invented certain new and useful Improvements in Tanning, of which the following is a s cification.

his invention relates to tanning; and it comprises a combined process of tanning wherein hide is first treated with a material containing chromic acid (CrO,) such as a chromate or bichromate to give a light im prefgnation and is thereafter treated with a sul te waste liquorpreparation or solution, having its normal constltuents substantially unaltered thereby reducing the chromic acid to the state of sesquioxld of chlomium or and advantageously to that of a chromate of chromium, said sulfite waste liquor also efiectin a tanning action; all as more fully hereina r set forth and as claimed.

It is of course well,known in the art to b tan hides with various chrome compounds. In one we of tanning, the hide is treated with a so ution containin a salt of the sesquioxid of chromium 130,), such as a with other bodies, salts of chromium sequi- 'oxid combined with weak acids, etc. In another method of tanning the hides are treated with a bichromate, such as potassium bichromate or sodium bichromate and thereafter with a reducing a nt ca 'able of oonverti chromium trioxi (C into, the sesquloxid, this a mineral salt suchas a yposulfite, a su te, etc. In the present method of tanning I use .a bichromate but instead. of employing a special mineral salt'to reduce the chromium trioxid or chromicacid to the sesquioxid I employ a body which itself has a tanning chrome alum together.

nt being usuall a.

the chromium troxid is reduced and the rest a remains as such. The result .of this is to roduce a chromate of-chromium in the hide.

he chromates of chromium are brownbodies which have, as I have found, a good tannin effect and are useful in accelerating and ai in subsequent tanning with other bodies. here the reduction of the bichromate goes so far as to produce sesquioxid of chromium, the hide is left, at this stage, with a bluish or greenish tinge but where the reduction is only partial and a chromate of chromium is formed in the hide. the color is brownish.

In the manufacture of paper pulp by the sulfite process, Wood is digested under pres sure wlth a solution of calcium (or calcium and magnesium) bisulfite. In the digestion various reactions go on by virtue of which about onehalf {the wood. the socalled lignone, goes into solution by uniting with the acid sulfite to form new solule organic bodies. The rest of the wood, the cellulose, remains undissolved as ordi-' nary paper pulp. For the sake of a name, the bodies found in the solution, the sulfite waste liquor are often termed 1i nosulfonates. Where the original sulfite hquor is a solutionof acid sulfite of calcium, the waste sulfite liquor is regarded as a solution of lignosulfonates of calcium. Where. as is often the case, the original sulfite liquor contains both magnesium and calcium acid sulfites, the characteristic bodies of the waste sulfiteliquor are regarded as a mixture of magnesium and calcium hgnosulfonates.

As the liquor leaves the digester it is rather weak and somewhat acid; containing a small fraction of a percent. of unchanged sulfurous acid or acid sulfite. The acidity is not great but some acidity exists. As a rule this liquid is not of a concentrated nature,

containing only a few or cent. of solid mat-v ter. Its density may e from 3 to,5 or 6 Baum. From this liquid various tanning 100 preparations can be made. 'One such preparation which finds extensive sale on the market ismade by simply neutralizing the raw liquor and evaporating in 'vacuo to a rather high density, usually around 30 105 Baum, (Patent 833,634) this giving a solution of the" essential substances of waste sulfiteliquor chemically unchanged. Alone, the raw sulfite liquor is not readily concentrated by heat without far-going decomposi- 1 I I prefer a de tion and loss of tanning bodies but if preliminarily somewhat neutralized it may be readily evaporated without substantial loss .of valuable constituents. 'Other tanning preparations are made from the concentrated liquor so prepared by treating it with a sulfate of a sesquioxid having tanning properties, that is sulfate of iron, sulfate of alumina or'sulfate of chromium. The lignosulfate of lime by doubledecomposition gives insoluble sulfate of lime which precipitates and a soluble llgnosulfate of iron, aluminum or chromium as the case may be. These'preparations are usually somewhat acid to litmus and do not give precipitates with metal salts. Other tanning preparations are made by treating theraw liquor with a little sulfuric acid and bisulfate of soda, thereby removing the lime as sulfate and leaving a liquid containing hgnosulfonic acid.

In the present invention a hide after the usual beam house preparation is first given a light impre ation with a solution ofa bichromate. ither the bichromate ofpotassium or bichromate of sodium may be used, although I find the latter more advanta eous for several reasons. Chromic acid ((JrQ may be used but is ordinarily more expensive. In order to assist the penetration of the bichromate into the hide it is useful to employ a little aluminum sulfate. and magnesium sulfate (Epsom salts) in the solution. A desirable bath for the present purposes may be made by dissolvin sodium bichromate in water to give a so ution of about 1 per cent.; astrength suflicient to give a light impregnation. In this solution may be dissolved 2 r cent. of aluminum sulfate and 3 .per cent. of Epsom salts. The hide is immersed in or wetted with the bichromate solution for a length of time sufiicient to secure good penetration; ordinarily two or three days. It is then removed from the chrome solution and treated with a slightly acid sulfite waste liquor preparation for four or fivedays. The greater the acidity the further the reduction of the chromium will go. of acidity of say 0.6 or 0.7 per cent., as t is causes only a partialreduction, forming chromate or chromium instead of reducing to sesquioxid. In addition to rechromate,

ducing the chromium the solution of the sulfite waste liquor also tans. I therefore obtain what may be called a combination tanning; a tanmng by reduced chromium (as chromium' sesquioxid or as chromate of chromium) and a tannin by the sulfite waste liquor. If the leat er is to be for harness and like purposes no further tanning'may be necessary. If .it is to be used for sole leather or similar purposes, I find it best to follow with another tanning operation. For this final tanning I may use a strong waste sulfite liquor such as the commercial 30 Baum preparations or another tanning material. ariousmixtures of conlcentrated waste sulfite liquor with other tanning material, such as oak, quebracho, mangrove, chestnut, -etc., may be employed.

What I claim is:-

1. The process of tanning which comprises treating a' hide with a solution of hichromate to produce a light impregnation and then effecting reduction of chromic acid to chromate of chromium in the hide and tanning by treating with a sulfite waste liquor material contain' its normal constituents substantiall unc anged.

2. The process 0 tanning which comprises treating a hide with a solution of hichromate containing aluminum sulfate and magnesium sulfate, and then effecting reduction in. the hide and tanning by treating with a sulfite waste liquor material.

3. The process of tanning which comprises lightly impregnating a hide with bichromate then reducing in the hide and tanning with a sulfite waste liquor material containing its normal constituents substantially unchanged, and eifecting a further tannin with a tanning extract.

4. T e process of tanning which comprises lightlg impregnating a hide with bit en reducing chromic acid .to chromate of chromium in the hide and tanning with a sulfite waste liquor material, and eifecting a further tanning with a tanning extract comprising a waste sulfite liquor preparation. I

In testimony whereof, I aflix my signature hereto.

JOHN K. 'TULLIS.

5 c Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,390,7 35, granted September 13, 1921, upon the application of John K. Tullis, of Nevt York, N. Y., for an improvement in Tanning, errors appear in the printed specification requiring correction as follows: Page 2, line 85, claim 2, after the word "material and before the period insert the phrase containing its normal constituents substantially unchanged,-

I same page, line 97 claim 4, after the word material and before the comma insert the phrase containing its normal constituents substantially unchanged; and that the said Letters Patent should be read with these corrections therein that the same may conformto the record of the case in the Patent Office.

Signedand sealed this 16th day of May, A. D., 1922.

[SEAL] KARL FENNING,

Acting Oonmaksiomr of Patents. 

